1. Field
This application relates to sailboards or windsurfing apparatus, specifically to those equipped with hydrofoils for providing vertical lift.
2. Prior Art
Numerous attempts have been made to equip a sailboard or windsurfing apparatus with hydrofoils providing vertical lift. The purpose of this is to reduce the effect of small waves and chop, which makes the ride smoother. In addition to being more comfortable for the user, a smoother ride could potentially enable higher speeds to be reached due to the lessened interference from water surface disturbances. Hydrofoils, along with their supporting structures, may also experience less drag than planing boards, though this is not guaranteed for all designs.
Some implementations of the hydrofoil sailboard concept are disclosed in U.S. patents, early examples of which are U.S. Pat. No. 4,508,046 (1985) and U.S. Pat. No. 4,715,304 (1987). Most designs use two hydrofoils mounted respectively at the front and the rear of the board. These hydrofoil sailboards tend to suffer from greater lateral instability compared to non-hydrofoil sailboards, because while the board is lifted clear of the water the hydrofoils and their supporting structures provide less resistance to rolling than a planing board does. Since the mast foot is a universal joint capable of tilting in any direction, the only way to prevent the board from rolling excessively is by careful control on the part of the user. This makes hydrofoil windsurfing much more difficult than conventional windsurfing. Thus the addition of hydrofoils has tended to result in increased difficulty of use, to an extent disproportionate to its advantages. This is likely the reason hydrofoil sailboards have not come into use and have not been sustainable as a marketed product.
One popular configuration of hydrofoils is known as the canard configuration, which comprises a hydrofoil for providing most of the vertical lift, and a surface tracking body capable of planing on the surface, the surface tracking body is positioned forward of the hydrofoil and connected to the hydrofoil through a arm, such that the angle of attack of the hydrofoil is continuously adjusted in order to maintain an approximately constant altitude. This configuration has been used in various watercraft, including U.S. Pat. No. 6,468,118 by the present inventor.
Incidentally, since a hydrofoil sailboard is intended to be lifted on the hydrofoils during normal operation, it is unnecessary for the buoyant body to be board shaped, and the width required to achieve that shape becomes superfluous.